Mutations of the antioxidant enzyme Cu,Zn SOD(SOD1) are responsible for about 20 percent of familial amyotrophic lateral sclerosis (FALS). More than 50 different SOD1 mutations have been identified. The process by which mutant SOD1 causes toxicity is not known, but all the mutants have a common property of binding copper and scavenging free radicals. Aberrant copper regulation has been suggested as one possible toxic property of mutant SOD1. Copper trafficking in mammalian cells is highly regulated. CCS is a newly cloned copper chaperone that functions to deliver copper specifically to SOD1, including mutant SOD1. In this proposal, we will investigate the biology of this new protein and evaluate its possible role in the neurotoxicity of mutant SOD1-mediated motor neuron degeneration. Preliminary studies suggest that CCS is commonly associated with SOD1 and that abnormal intracellular inclusions in transgenic models of ALS may reflect CCS-SOD1 aberrant interactions. We propose a systematic study of CCS, first by generating several oligo peptide antibodies to investigate the cellular and ultrastructural localization of CCS in both human and murine tissues. We hypothesize that CCS distribution will closely follow that of SOD1. Next, we will determine if CCS is associated with cellular abnormalities in transgenic mice expressing mutant SOD1. We will examine and compare neural tissue, obtained over time, from transgenic mice with two different SOD1 mutations (G93A and G85R) which exhibit different time courses of neurodegeneration and neuropathology. Thirdly, we will also examine CNS tissue from sporadic and familial ALS to determine if there aggregates of CCS the disease? Finally, we will test the hypothesis that CCS can contribute to, or cause, the intracellular inclusions seen in ALS models, and that it plays a direct role in mutant SOD1 motor neuron toxicity. Overall, these experiments will help test the hypothesis that 1) CCS is responsible for the cytoplasmic aggregates in astrocytes and neurons, and 2) that CCS participates in mutant SOD1 mediated neurotoxicity.